EDP Sciences
Free access
Volume 437, Number 1, July I 2005
Page(s) 285 - 296
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20042572

A&A 437, 285-296 (2005)
DOI: 10.1051/0004-6361:20042572

Atmospheric dynamics in carbon-rich Miras

II. Models meet observations
W. Nowotny1, T. Lebzelter1, J. Hron1 and S. Höfner2

1  Institut für Astronomie der Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria
    e-mail: nowotny@astro.univie.ac.at
2  Departement of Astronomy and Space Physics, Uppsala University, Box 515, 75120 Uppsala, Sweden

(Received 17 December 2005 / Accepted 28 February 2005)

Originating in different depths of the very extended atmospheres of AGB stars, various molecular spectral lines observable in the near-infrared show diverse behaviours and can be used to probe atmospheric dynamics throughout the outer layers of these pulsating red giants. In Nowotny et al. (2005b, A&A, 437, 273, Paper I) time series of synthetic high-resolution spectra were presented, computed from a dynamic model atmosphere for a typical carbon-rich Mira. In this work, line profile shapes, their variations during the lightcycle and radial velocities derived from wavelength shifts are analyzed and compared with results from observed FTS spectra of the C-rich Mira S Cep and other Miras. It is found that the global velocity structure of the model is in qualitative agreement with observations. Radial velocities of molecular lines sampling different layers behave comparably, although some differences are apparant concerning absolute values. A correction factor of $p \approx 1.36$ between measured RVs and actual gas velocities is derived for CO  $\Delta v=3$ lines. It is shown that dynamic model atmospheres are capable of reproducing Mira spectra without introducing an additional "static layer" proposed by several authors.

Key words: stars: late-type -- stars: AGB and post-AGB  -- stars: atmospheres -- stars: carbon -- infrared: stars -- line: profiles

SIMBAD Objects in preparation

© ESO 2005